In the thermal cleaning of an exhaust fluid stream using regenerative heat exchangers, two or more containers can be employed, each of which contains heat storage material through which the exhaust fluid stream flows. The ends of each container are connected to one another by at least one combustion chamber. The noxious exhaust fluid stream which contains combustible, gaseous or vaporous components such as solvent vapors, and which is typically withdrawn from a production or refining process, first flows through one of the containers, is heated by a previously heated-up heat storage material, and then passes into the combustion chamber in which the noxious components, if necessary, with the addition of a fuel, are oxidized at temperatures of, for example, between 800.degree. and 1,000.degree. C., in particular, to form CO.sub.2 and H.sub.2 O. The thus cleaned, hot exhaust fluid stream (the so-called purified gas) then flows through the other container and heats the heat storage material contained therein. Each of the containers is alternately supplied with an inlet exhaust fluid stream to be cleaned and a purified exhaust fluid stream to be cooled. A flushing operation is usually carried out between these two operations, i.e., the container which has been previously supplied with inlet exhaust fluid stream to be cleaned is flushed with purified gas or fresh air to prevent noxious components in the inlet exhaust fluid stream from being carried into the purified exhaust fluid stream. Alternatively, the noxious gas volume is aspirated from the pertinent container and conducted to the inlet exhaust fluid stream yet to be cleaned.
The exhaust fluid stream employed herein is principally a gaseous stream which contains combustible, gaseous or vaporous components. The exhaust fluid stream may also be a liquid stream which contains combustible, gaseous or vaporous components.
The alternating operation of a container as a device for heating the exhaust fluid stream to be cleaned, as a device to be heated by the hot purified gas, or as a container from which the noxious residual gas is to be removed, is realized in such known apparatus by an inlet flap, an outlet flap and a withdrawal or flushing gas flap or by a rotary slide which assumes the functions of these flaps each being associated with each container.
When flaps are used, considerable driving energy is required for actuation of the flaps, and, in addition, high control component costs. Since the flaps are normally actuated with a compressed fluid stream, they open and close abruptly without any special additional devices and thus cause strong pressure fluctuations in the installation which can have a negative effect on the process preceding the cleaning of the exhaust fluid stream. Also, during the switching of the flaps emission peaks occur in the purified gas (higher proportions of noxious substances) as a result of the brief occurrence of bypass short circuits between exhaust fluid stream to be cleaned which is supplied to the installation and purified gas which is removed from the installation.
The use of a rotary slide requires the containers accommodating the heat storage materials to have circular-cylindrical shapes. Such a requirement makes it virtually impossible to use commercially available, ceramic honeycomb bodies (which are block-shaped) for the heat storage materials. Bulk material must therefore be employed as the heat storage material, but this results in a pressure loss which is approximately ten times greater than the pressure loss caused by honeycomb bodies. Such a large pressure drop has a negative effect on the consumption of electric energy for a ventilator with which the exhaust fluid stream to be cleaned is conveyed into the installation.
The object underlying the present invention is to provide an apparatus for thermally cleaning exhaust fluid stream, the basic construction of which enables the apparatus to be readily designed such that with it at least some of the disadvantages of the known apparatus explained hereinabove are avoided.